Typical commercial-grade activated carbon air filters are designed to remove many common airborne contaminants but are not designed to effectively protect against many deadly CBRN agents that could potentially be used during acts of terrorism. These CBRN agents can only be effectively removed by using specially treated carbon "adsorption" filters.
The most effective activated carbon adsorption filter medium to protect against the effects of toxic CBRN agents is a highly activated carbon with metal coating enhancement. The two most common metal coatings used in the western world are ASC-TEDA (copper-silver-chromium-trietheylenediamine) and ASZM-TEDA (carbon-activated, impregnated copper-silver-zinc-molybdenum-trietheylenediamine) military-grade activated impregnated carbon. ASC-TEDA is no longer used in the U.S. because of its chromium content. The ASZM-TEDA coating is patented by the U.S. Army and offers the best chemical protection available. It is the only grade of carbon deemed acceptable for collective and personal CBRN protection systems and devices by the U.S. Army.
A carbon adsorption filter removes molecules from the airstream by the process of adsorption, trapping molecules in the pores of the carbon granules. This system works best against large molecules, that is, chemicals of low vapor pressure. Activated carbon is an effective sorbent for removing a broad range of chemical vapors because of its extensive micro-porosity and range of pore sizes. Typically the pores in highly activated carbon have a total surface area of over 1,000-square-meters per gram.
Filtering chemicals of high vapor pressure—small molecules—requires a chemical reaction with impregnates (coatings) added to the carbon, as in ASZM-TEDA process carbon. These impregnates react with the toxic gas through the filter to form products that are either innocuous or that can be "grabbed," or adsorbed, and retained by the filter.
No filters available on the market provide protection from as wide a range of adsorbable chemicals and biological agents as HDT filters and filter systems. Through our Applied Research Center in Edgewood, Maryland, and joint development and testing efforts with the U.S. Army, HDT is continuing to develop effective filtration technology to protect against an even wider range of chemicals, including the most common and dangerous Toxic Industrial Chemicals/Toxic Industrial Materials (TIC/TIMs).
All HDT Homeland Security products and systems have been thoroughly tested for the effective removal of a wide range of CBRN agents, which comprise the greatest threat from either acts of terrorism or accidental release.